1. Field of the Invention
The present invention concerns an a-c magnet and, in particular, an a-c magnet having slots running transversely to the direction of the laminations in the surface of at least one pole and including a shorting ring arranged with its long edges in the slots.
2. Description of the Prior Art
In one known a-c magnet of the above-mentioned kind, the shorting ring is first placed in slots in the magnet. A calking tool is then set along the top side of the ring in the vicinity of the slots, and, simultaneously, a stamping tool is set along the outside of the parts of the walls which extend beyond the ring. The ring is then secured to the magnet by bending the wall parts in the direction toward the slots. During such action, the calking tool serves as a hold-down mechanism, thereby preventing the ring material from escaping outward when the wall sections are bent. With this technique, the hold-down force exerted by calking tool must be of such a magnitude as to cause the shorting ring to be deformed, otherwise the shorting ring will not rest on the slot bottom and will loosen and vibrate. In addition, using this technique the pole surface is altered by the bending of the wall parts, thereby necessitating an additional grinding operation in order to obtain a flat seating surface.
In another known technique, the shorting rings of an a-c magnet are secured in two slots whose vertical center lines intersect at least once, by elastic or plastic deformation. This technique requires the use of expensive stamping tools, and, moreover, presents problems for smaller cross sections as, in order to secure the ring, a certain amount of shorting ring material must be deformed.
It is an object of the present invention to provide an a-c magnet whose shorting ring is secured in a simple manner.